JP2000026857A - Hydrophilic surface treating agent and precoated fin for heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep hydrophilicity without sacrificing adherence when a press oil is coated by mixing a carboxymethyl cellulose salt, N-methylolacrylamide, polyacrylic acid, a Zr compound and polyethylene glycol, each mixing ratio being in a specific range. SOLUTION: A surface treating agent is obtained by mixing 0.1-2 wt.% of each a carboxymethyl cellulose sodium salt and a carboxymethyl cellulose ammonium salt, 0.2-4 wt.% of a N-methylolacrylamide, 0.05-1 wt.% of polyacrylic acid, 0.01-0.5 wt.% of a Zr compound and poloyethylene glycol having an average molecular weight of 300-400 wherein a solid ratio (a sum of the carboxymethyl cellulose/the polyethylene glycol) is 2/1-1/2. Thus obtained surface treating agent is coated on an anti-corrosive layer-laminated surface of an aluminum or an alloy thereof, baked at 170-240 deg.C to form a film having thickness of 0.1-1.0 g/m2 usable for a precoated fin material for a heat exchanger.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for imparting hydrophilicity to the surface of aluminum or an alloy thereof (hereinafter, also simply referred to as "aluminum material") used for manufacturing a radiation fin of a heat exchanger. The present invention relates to a pre-coated fin material for a heat exchanger, comprising a hydrophilic surface treating agent and an aluminum material to which hydrophilicity has been imparted using the treating agent.

[0002]

2. Description of the Related Art A precoated fin material for a heat exchanger made of an aluminum material is formed into a desired fin shape to be used as a heat radiating fin material for a heat exchanger in an air conditioner or the like installed in a building or an automobile. ing.

[0003] Further, such a pre-coated fin material for a heat exchanger is usually subjected to a coating treatment for imparting corrosion resistance for preventing the fin surface from being corroded by the generation of white rust. Coating treatment for imparting hydrophilicity to prevent heat exchange efficiency from decreasing due to moisture condensed on the fin surface closing the gap between the fins during air-conditioning equipment cooling operation etc. Is applied.

[0004] By the way, as a film treatment for imparting corrosion resistance and hydrophilicity as described above, conventionally, a corrosion resistant film is formed on a surface of an aluminum material by a chromate surface treatment agent, and then a silicate hydrophilic film is formed. Many methods of forming a film have been adopted. In this case, particularly with respect to hydrophilicity, excellent hydrophilicity can be obtained because the hydrophilic film is an inorganic film, but on the other hand, there is a problem that odor peculiar to an inorganic film such as silica is generated.

For this reason, conventionally, there has been proposed a technique of forming a hydrophilic film composed of an organic film in place of the hydrophilic film composed of the inorganic film. For example, Japanese Patent No. 2520308 (Japanese Unexamined Patent Application Publication No. 2-258874)
No.) includes 5 to 25 parts by weight of a sodium and / or potassium salt of carboxymethyl cellulose and 25% by weight of ammonium salt of carboxymethyl cellulose in terms of solid content.
５０50 parts by weight and N-methylolacrylamide 25〜
Hydrophilic surface treatment agent containing 1.5 to 15 parts by weight of polyacrylic acid and 0.6 to 9 parts by weight of zirconium compound (as Zr) based on 100 parts by weight of a total of 70 parts by weight After applying the surface treatment agent to the surface of the aluminum material after degreasing treatment (after forming a corrosion-resistant film if necessary) and baking, a hydrophilic film composed of an organic film is formed. Surface treatment agents and precoated fin materials are shown.

However, when an organic hydrophilic film made of the hydrophilic surface treating agent is formed, there is a new disadvantage that the hydrophilicity is not sufficient in terms of the durability. Also, when brazing a copper pipe for a refrigerant to a radiation fin made of a pre-coated fin material having such an organic hydrophilic film formed thereon, the heat of the brazing causes the hydrophilic film to burn and yellow. There is a problem that does. Further, when the precoated fin material on which the organic hydrophilic film is formed is press-formed, the fin material surface has a high friction coefficient due to the film, so that seizure easily occurs.

For the purpose of further improving the hydrophilicity and the like of such an organic hydrophilic film, for example,
JP-A-6-322552 discloses that, in terms of solid content, 5 to 25 parts by weight of sodium and / or potassium salt of carboxymethyl cellulose, 25 to 50 parts by weight of ammonium salt of carboxymethyl cellulose, and 25 to 50 parts by weight of N-methylolacrylamide 5 parts to 50 parts by weight of polyacrylic acid, 5 to 50 parts by weight of polyethylene oxide, and 0.6 to 9 parts by weight of a zirconium compound (as Zr) based on 100 parts by weight of a total of 70 parts by weight. There is disclosed a method for forming a hydrophilic film made of a surface treating agent by using the contained hydrophilic surface treating agent.

[0008] In the hydrophilic film formed by this hydrophilic surface treating agent, good hydrophilicity (persistence), water solubility and corrosion resistance are obtained by forming a complex between polyacrylic acid and polyethylene oxide. In addition, the alkali resistance is further improved by the inclusion of the zirconium compound.

However, in the case of a precoated fin material on which a hydrophilic film is formed by the new hydrophilic surface treating agent, when the press oil for press molding is applied, the hydrophilic property of the hydrophilic film is initially hydrophilic. There is a problem that it is lower than the properties. Moreover, after the press oil is applied, there is also a problem that the hydrophilicity persistence due to the hydrophilic film is reduced. In addition, the adhesion of the hydrophilic film tends to decrease particularly in a wet environment.

Japanese Patent Application Laid-Open No. Hei 9-14888 discloses that a hydrophilic film (for example, a film composed of a mixed paint of water glass and polyacrylic acid) is not impaired on the surface of an aluminum material after the film is formed. Polyethylene glycol having an average molecular weight of 200 to 3000 is used as a resin.
A fin material applied at 1 mg / dm ² or more has been proposed.

However, in the case of such a fin material in which a resin such as polyethylene glycol is merely applied on the hydrophilic film, although the press moldability is improved, the polyethylene glycol layer formed by applying the resin is improved. Is only physically on the surface of the hydrophilic film, and generally has poor adhesion to the film. For this reason, when advanced processing contents such as ironing are added during press forming,
There is a problem that the polyethylene glycol layer is peeled off and the press oil comes into direct contact with the surface of the underlying hydrophilic film on the part where the polyethylene glycol layer is peeled off, and the hydrophilicity of such film is reduced. In addition, when the polyethylene glycol layer is peeled off as described above, press formability also decreases. In addition, there is a problem that workability is reduced due to an increase in the number of coating steps for coating a resin such as polyethylene glycol.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a hydrophilic film in which a press oil is applied without impairing the adhesion of a hydrophilic film. An object of the present invention is to provide a hydrophilic surface treatment agent and a pre-coated fin material for a heat exchanger, which can suppress deterioration of the properties and can continuously obtain excellent hydrophilicity.

[0013]

Means for Solving the Problems The hydrophilic surface treating agent of the present invention, which can achieve the above-mentioned objects, comprises 0.1 to 2% by weight of sodium salt of carboxymethyl cellulose and 0.1 to 2% by weight of ammonium salt of carboxymethyl cellulose. 2% by weight
And N-methylolacrylamide 0.2 to 4% by weight
And 0.05 to 1% by weight of polyacrylic acid and 0.01 to 0.5% by weight of a zirconium compound (as Zr) and a polyethylene glycol having a weight average molecular weight of 300 to 400, and a solid content ratio ( (Total of sodium salt and ammonium salt of carboxymethylcellulose / polyethylene glycol) in a ratio of 2/1 to 1/2.

The precoated fin material for a heat exchanger according to the present invention is characterized in that the surface of aluminum or an alloy thereof on which a corrosion-resistant film is formed has a sodium salt of carboxymethyl cellulose of 0.1 to 2% by weight and an ammonium salt of carboxymethyl cellulose. 0.1 to 2% by weight, 0.2 to 4% by weight of N-methylolacrylamide, 0.05 to 1% by weight of polyacrylic acid, and 0.01 to 0.5% by weight of a zirconium compound (as Zr) And a polyethylene glycol having a weight average molecular weight of 300 to 400 in a solid content ratio (total of sodium salt and ammonium salt of carboxymethyl cellulose / polyethylene glycol) in a ratio of 2/1 to 1/2. The film thickness obtained by applying a surface treatment agent and baking at a temperature of 170 to 240 ° C. is 0.1 to In which the hydrophilic coating of .0g / m ² is formed.

Here, the sodium salt of carboxymethyl cellulose in the hydrophilic surface treatment agent is contained in the treatment agent in an amount of 0.1 to 2% by weight, preferably 0.25 to 1.5% by weight.
% By weight. If the content is less than 0.1% by weight, there is a problem that the initial hydrophilicity is good but the hydrophilicity persistence is low. On the other hand, if it exceeds 2% by weight, the hydrophilicity persistence is good. However, there is a problem that the workability is remarkably reduced because the viscosity becomes too high.

The ammonium salt of carboxymethyl cellulose is contained in the surface treating agent in an amount of 0.1 to 2% by weight, preferably 0.25 to 1.5% by weight. If the content is less than 0.1% by weight, there is a problem that the initial hydrophilicity is lowered. On the other hand, if it exceeds 2% by weight, the hydrophilicity is improved, but depending on the processing temperature at the time of baking. There is a problem that the ammonium component remaining undecomposed in the film is released in a subsequent step, or the ammonium component released at the time of baking is adsorbed by the film to emit an ammonia odor.

The N-methylol acrylamide is contained in the surface treatment agent in an amount of 0.2 to 4% by weight, preferably 0.5 to 2% by weight.
% By weight. If the content is less than 0.2% by weight, there is a problem that a film is easily damaged when there is a press forming process with a high ironing rate, and conversely, 4% by weight.
If it exceeds, the film becomes too hard and easily peels off, or excessive N-methylolacrylamide in the components does not become a film at the time of baking and the monomer evaporates as it is.

The polyacrylic acid is contained in the surface treating agent in an amount of 0.05 to 1% by weight, preferably 0.2 to 0.5% by weight.
included. When this content is less than 0.05% by weight,
When there is a press forming process having a high ironing rate, there is a problem that the film is easily damaged, and when it exceeds 1% by weight, there is a problem that the hydrophilicity is reduced.

The above zirconium compound is contained in the surface treating agent in an amount of 0.01 to 0.5% by weight as Zr, preferably 0.1 to 0.5% by weight.
It is contained in an amount of 0.3 to 0.2% by weight. If this content is less than 0.01% by weight, there is a problem that the curing of polyacrylic acid is insufficient and the corrosion resistance is lowered, while 0.5% by weight
If it exceeds 300, there is a problem that the film is too hard and the workability is lowered.

The polyethylene glycol has a weight average molecular weight of 300 to 400. This molecular weight is 3
If it is less than 00, it becomes impossible to sufficiently suppress the decrease in hydrophilicity of the hydrophilic film due to the application of press oil, and if it exceeds 400, the amount remaining in the hydrophilic film of polyethylene glycol increases, The adhesion of the film is reduced. Further, the polyethylene glycol is contained in the surface treatment agent at a solid content ratio of 2/1 to 1/2, preferably 1: 1.
/ 1 to 1 / 1.8. When the solid content ratio exceeds 2/1 (ie, when the amount of polyethylene glycol is too small), the decrease in hydrophilicity due to press oil cannot be sufficiently suppressed, and when the solid content ratio is less than 1/2 (ie, when polyethylene glycol is too small). If the glycol content is too high), the film softens and becomes easily damaged.

Such a low-molecular-weight polyethylene glycol bleeds on the surface side of the hydrophilic film and exists in a layered form, and is formed by the baking and drying agent after the hydrophilic surface treatment agent is applied. It is presumed that it prevents the hydrophilic coating from being directly exposed to the heated air. It is thought that this prevents the hydrophilicity of the resin component in the coating from directly touching the heated air to change the orientation state, thereby preventing the hydrophilicity of the coating surface from being reduced. In addition, the film made of this surface treatment agent not only has the surface of the film covered with polyethylene glycol, but also has a stepwise increase in the concentration of polyethylene glycol from the inside of the film to the surface layer. It is considered to be in shape. As a result, the effect of maintaining the hydrophilicity of the fin material and the effect of improving the moldability are increased as compared with the case where the polyethylene glycol is simply applied to the surface of the hydrophilic film as in the above-described conventional example. In addition, the low molecular weight polyethylene glycol used in the present invention is finally easily removed (dissolved) by dew water generated in the fin material.

In addition to the above-mentioned essential components, the hydrophilic surface treating agent includes, for example, a blue pigment which gives a refreshing feeling to the fin material, various coloring pigments which give an interior decoration feeling, and fungi and mold. An antibacterial / antifungal agent for suppressing the generation and propagation of microorganisms such as the above, or an inhibitor for improving the corrosion resistance of the fin material may be contained. However, other surfactants than the low-molecular-weight polyethylene glycol are not contained. This is because, in the case of a hydrophilic surface treatment agent containing another surfactant, the treatment bath foams at the time of application to an aluminum material, and the workability at the time of application is reduced.

Further, the precoated fin material for a heat exchanger of the present invention is obtained by applying a hydrophilic surface treating agent having the above-mentioned structure to a surface of an aluminum material on which a corrosion-resistant film is formed in advance, and then applying a temperature of 170 to 240 ° C. To form a hydrophilic film having a thickness of 0.1 to 1.0 g / m ² . As the aluminum material, a material obtained by forming a corrosion-resistant film by chromate treatment or the like after degreasing if necessary. The corrosion-resistant coating preferably has a thickness of 0.2 to 1.2 g / m ² .

The application of the hydrophilic surface treatment agent is performed by a coating method such as a roll coating method, a bar coating method, a spray method, and a dipping method. At this time, the hydrophilic surface treatment agent is used after being appropriately diluted so as to have a predetermined concentration. On the other hand, if the baking temperature (heating temperature) is lower than 170 ° C., there is a problem that the adhesion of the obtained film becomes insufficient. On the other hand, if the temperature exceeds 240 ° C., the curing reaction of the film proceeds more than necessary, causing the film to become brittle, or the hydrophilicity is degraded due to the decomposition of the hydrophilic group, and furthermore, the extreme surface layer of the low molecular weight polyethylene glycol. There is a problem that bleeding to the portion causes the destruction of the original inclined film and the like. Further, when the film thickness is less than 0.1 g / m ² , there is a problem that the dispersion of hydrophilicity between lots is large, and the deterioration of the hydrophilicity with time is large. m
^If it exceeds ² , not only the further improvement in hydrophilicity cannot be expected, but rather, the scorching of the film due to the heat at the time of brazing the copper tube for the refrigerant becomes noticeable, and the cost increases as the film thickness increases. And other problems occur.

The precoated fin material thus obtained is obtained by applying volatile press oil for press forming to the surface of the precoated fin material and then subjecting the surface to a forming process such as slitting or corrugating. A fin material for a heat exchanger having a desired fin shape is obtained.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to examples.

First, as a hydrophilic surface treatment agent, sodium salt of carboxymethyl cellulose [CMC1290, manufactured by Daicel Chemical Industries, Ltd.] 0.25% by weight, ammonium salt of carboxymethyl cellulose [CMC D, manufactured by Daicel Chemical Industries, Ltd.] -10 L] 0.75% by weight, N-methylol acrylamide [manufactured by Soken Chemical Co., Ltd .: N-MA
MP] 1.0% by weight, polyacrylic acid (Accumer 1510, manufactured by Rohm and Haas Co., Ltd.) 0.075% by weight, H ₂ ZrF ₆ as a zirconium compound [Nippon Light Metal Co., Ltd.
A plurality of types containing 0.1% by weight (as Zr) and polyethylene glycol (PEG) having a content and an average molecular weight shown in Table 1 [manufactured by NOF Corporation: Nissan polyethylene glycol] Prepared. In addition to these essential components, in addition to the above-mentioned essential components, these surface treatment agents include nonionic agents commercially available as antiseptic and fungicide agents for paints [Daiwa Chemical Industry Co., Ltd.] Manufacture: Amorden K-3] 0.05% by weight (however, no surfactant is contained).

Next, a plurality of aluminum plates (JIS A 1050, thickness 100 μm) were degreased as an aluminum material for applying each of these hydrophilic surface treatment agents, and the surface after the degreasing was particularly treated. A corrosion-resistant treatment agent similar to the corrosion-resistant hydrophilic film treatment agent described in Japanese Patent Publication No. 3-48273 (column 9, lines 17 to 29) is applied by a bar coater, and PMT (Peak Metal Temperature) 2 of the aluminum plate is applied.
What was dried at a temperature of 30 ° C. for 15 seconds to form a corrosion-resistant film was prepared.

Then, the same hydrophilic surface treating agent is applied to the surface of each aluminum plate by a bar coater in the same amount, and dried at a PMT of 170 to 240 ° C. for 20 seconds to obtain a film thickness of 0.1 μm. A hydrophilic film of 7 g / m ² was formed.

The following initial hydrophilicity test, hydrophilicity persistence test and film adhesion test were carried out using each of the thus obtained aluminum plates (hereinafter also simply referred to as "test pieces").

In the "initial hydrophilicity test", a test piece was not coated with press oil (before coating) and a test piece was coated (after coating).
I went separately. The application of the press oil was performed by applying a volatile press oil (manufactured by Idemitsu Kosan Co., Ltd .: Daphne Punch Oil AF2C) and then drying by heating at 180 ° C. for 3 minutes. 2 μl of pure water was dropped on each of the test pieces in a horizontal state before and after the press oil was applied, and the contact angle of the water droplet was measured by a contact angle meter (manufactured by Kyowa Interface Chemical Co., Ltd .: CA-A).
(Type). FIG. 1 shows the measurement result of the test piece before application, and FIG. 2 shows the measurement result of the test piece after application. In addition, the obtained measurement results (contact angles) were evaluated according to the following criteria, and the results are shown in Table 1. ◎: less than 10 ° ○: 10 ° to less than 20 ° △: 20 ° to less than 30 ° ×: 30 ° or more

"Hydrophilic persistence" was carried out, as in the case of the above-mentioned initial hydrophilicity test, separately for a test piece to which no press oil was applied and a test piece to which a press oil was applied. The same applies to the application of press oil. Each test piece before and after applying the press oil was dried under the condition that it was immersed in pure water for 100 hours and then left at room temperature for 24 hours. The contact angle was measured. FIG. 3 shows the measurement result of the test piece before application, and FIG. 4 shows the measurement result of the test piece after application. In addition, the obtained measurement results (contact angles) were evaluated based on the following criteria, and the results are shown in Table 1. ◎: less than 20 ° ○: 20 ° or more and less than 30 ° Δ: 30 ° or more and less than 40 ° ×: 40 ° or more

The "coating adhesion test" was carried out by dividing the test piece into a dry state (during drying) and a wet state (when wet). First, in the test at the time of drying, the surface of the film of the test piece in a dry state was wiped with a Kimwipe (load: 100 g /
rubbing at 20 cm ² ), and the peeling state of the film at that time was examined. Then, the obtained results (adhesion of the film) were evaluated according to the following criteria, and the results are shown in Table 1. ◎: not peeled off (film peeling area ratio of less than 5% based on entire rubbing area) ○: hardly peeled off (peeling area ratio of 5% or more and 20%)
Δ: Partially peeled (peeling area ratio 20% or more and 50%)
×): easily peeled (peeling area ratio 50% or more)

On the other hand, in the wet test, pure water was dropped on a test piece, and the surface of the film wet with the pure water was put on a finger (load: 100 g).
/ Cm ² ) 20 times, and the solubility of the film at that time was examined. Then, the obtained results (the solubility of the film) were evaluated based on the following criteria, and the results are shown in Table 1. ◎: Not dissolved (less than 5% of film dissolution area relative to entire rubbing area) ○: Almost not dissolved (dissolution area ratio 5% or more and 20%)
Δ: partially dissolved (dissolution area ratio 20% or more and 50%)
×: easily dissolved (dissolution area ratio 50% or more)

The evaluations obtained in each test were further comprehensively evaluated according to the following criteria, and the results are shown in Table 1. ◎: All evaluation results are ○ or more (○ or）). ：: All evaluation results are △ or more (△, 又 は or ◎). △: One of all evaluation results is x. ×: When there are two or more × in all evaluation results

[0036]

[Table 1]

From the results shown in Table 1, the surface treatment containing low-molecular-weight polyethylene glycol having a molecular weight of "300" or "400" in a ratio of 1 to 2 times the total of the sodium salt and the ammonium salt of carboxymethyl cellulose. When a hydrophilic film made of an agent is formed (specimen N
o. 10, 11, 17, 18, 24, and 25), it can be seen that the decrease in hydrophilicity due to the application of press oil is small, and that good hydrophilic persistence and film adhesion are obtained. In addition, as for the hydrophilicity, it can be seen that better results are obtained as the content of the low-molecular-weight polyethylene glycol is increased. It can be seen that the film adhesion tends to gradually decrease as the content increases.

[0038]

As described above, according to the hydrophilic surface treating agent and the precoated fin material for heat exchanger of the present invention,
Good adhesion of the hydrophilic film is obtained, and excellent hydrophilicity can be reliably and continuously obtained even when press oil is applied. Therefore, when a fin material for a heat exchanger made of an aluminum material is manufactured using such a surface treatment agent or a pre-coated fin material, there is almost no decrease in heat exchange performance due to dew condensation on the fin surface, and good and stable. It is possible to obtain a fin material in which the heat exchange is realized for a long time.

[Brief description of the drawings]

FIG. 1 is a graph showing measurement results of an initial hydrophilicity test before press oil application.

FIG. 2 is a graph showing measurement results of initial hydrophilicity after press oil application.

FIG. 3 is a graph showing the measurement results of hydrophilicity persistence before press oil application.

FIG. 4 is a graph showing the measurement results of hydrophilic persistence after press oil application.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4H025 AA12 AA13 AA36 AA37 AB00 AC01 4K062 AA01 BA20 BB07 BB15 BC07 BC09 BC22 CA04 EA02 FA20 GA10

Claims (2)

[Claims] 1. A sodium salt of carboxymethylcellulose 0.1 to 2% by weight, an ammonium salt of carboxymethylcellulose 0.1 to 2% by weight, N-methylolacrylamide 0.2 to 4% by weight, and polyacrylic acid 0%. 0.05 to 1% by weight and 0.01 to 0.5% by weight of a zirconium compound (as Zr), and a polyethylene glycol having a weight average molecular weight of 300 to 400 in a solid content ratio (sodium salt of carboxymethyl cellulose and (Hydrogen surface treatment agent) characterized in that it is contained at a ratio of 2/1 to 1/2 (total of ammonium salts / polyethylene glycol). 2. The method according to claim 1, wherein the surface of the aluminum or the alloy on which the corrosion-resistant coating is formed has a sodium salt of carboxymethylcellulose of 0.1 to 2% by weight, an ammonium salt of carboxymethylcellulose of 0.1 to 2% by weight, 0.2 to 4% by weight of methylol acrylamide, 0.05 to 1% by weight of polyacrylic acid, and a zirconium compound (Zr
(Polyethylene glycol) having a weight-average molecular weight of 300 to 400 and a solid content ratio (total of sodium and ammonium salts of carboxymethyl cellulose / polyethylene glycol) of 2/1. A hydrophilic film having a thickness of 0.1 to 1.0 g / m ² is formed by applying a hydrophilic surface treating agent contained in a ratio of １ ／ to １ ／ and baking at a temperature of 170 to 240 ° C. A precoated fin material for a heat exchanger.